Electro-oxidation of methanol and ethanol using a Pt-RuO2/C composite prepared by the sol-gel technique and supported on boron-doped diamond

A detailed description of the preparation, characterization and electrochemical performance towards methanol and ethanol oxidation in acid medium of a platinum–ruthenium oxide carbon powder composite is presented here. The composite was prepared by the sol–gel technique and fixed on the surface of a boron-doped diamond (BDD) electrode. The physical characterization by XRD and EDX revealed the crystalline nature of the catalysts particles having an average size of 7.2 nm and a mass ratio of practically 1:1 for Pt and Ru, in accordance with the preparation conditions. Initial electrochemical experiments using also glassy carbon as the substrate for the composite showed that BDD has a superior performance, probably related to the very low capacitive currents of that material. The oxidation of methanol and ethanol in H2SO4 solutions was studied by cyclic voltammetry, Tafel plots and chronoamperometry and the results were compared to those obtained using a commercial Pt/C powder composite under the same conditions. In all cases, the Pt–RuO2/C composite showed larger anodic current densities and increased stability than the other material thus confirming the suitability of the simple and straightforward preparation technique for the catalysts.